Discovery of Apis mellifera filamentous virus in the blue orchard bee: Characterization of impacts and interactions with an organosilicone surfactant

Abstract While RNA viruses have received attention in impacts on bee health, research is limited for DNA viruses. DNA viruses, such as Apis mellifera filamentous virus (AmFV), have been identified in solitary bees; but infection dynamics and impacts are not well studied. We detected AmFV in diapausing Osmia lignaria adults and dead larvae from wild populations using metagenomic sequencing. Finding AmFV in diapausing adults in cocoons indicated an active AmFV infection. Unmodified larval provisions from nests had significant levels of AmFV, suggesting virus transmission may occur via fecal/oral routes via pollen. Using established rearing methods, we fed O. lignaria larvae AmFV and monitored survival, development, and adult weight metrics. Increased amounts of AmFV in larval provisions resulted in increased mortality. Co-exposure to an organosilicone surfactant (OSS) in provisions synergistically increased AmFV titers in larvae and adults, indicating that agrochemicals could affect viral infections. With increased development time from 2nd instar to pupation, bees of both sexes weighed more; however, male and female bees were impacted differently by AmFV and OSS. OSS plus AmFV exposure significantly increased the time to pupation in female bees. Male bees exposed to OSS weighed more. These results provide crucial insights into AmFV disease dynamics.